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Subject[PATCH v2 3/5] nohz: cpu_isolated strict mode configurable signal
Date
Allow userspace to override the default SIGKILL delivered
when a cpu_isolated process in STRICT mode does a syscall
or otherwise synchronously enters the kernel.

In addition to being able to set the signal, we now also
pass whether or not the interruption was from a syscall in
the si_code field of the siginfo.

Signed-off-by: Chris Metcalf <cmetcalf@ezchip.com>
---
include/uapi/linux/prctl.h | 2 ++
kernel/time/tick-sched.c | 15 +++++++++++----
2 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/include/uapi/linux/prctl.h b/include/uapi/linux/prctl.h
index 0c11238a84fb..ab45bd3d5799 100644
--- a/include/uapi/linux/prctl.h
+++ b/include/uapi/linux/prctl.h
@@ -195,5 +195,7 @@ struct prctl_mm_map {
#define PR_GET_CPU_ISOLATED 48
# define PR_CPU_ISOLATED_ENABLE (1 << 0)
# define PR_CPU_ISOLATED_STRICT (1 << 1)
+# define PR_CPU_ISOLATED_SET_SIG(sig) (((sig) & 0x7f) << 8)
+# define PR_CPU_ISOLATED_GET_SIG(bits) (((bits) >> 8) & 0x7f)

#endif /* _LINUX_PRCTL_H */
diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index 273820cd484a..772be78f926c 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -441,11 +441,18 @@ void tick_nohz_cpu_isolated_enter(void)
}
}

-static void kill_cpu_isolated_strict_task(void)
+static void kill_cpu_isolated_strict_task(int is_syscall)
{
+ siginfo_t info = {};
+ int sig;
+
dump_stack();
current->cpu_isolated_flags &= ~PR_CPU_ISOLATED_ENABLE;
- send_sig(SIGKILL, current, 1);
+
+ sig = PR_CPU_ISOLATED_GET_SIG(current->cpu_isolated_flags) ?: SIGKILL;
+ info.si_signo = sig;
+ info.si_code = is_syscall;
+ send_sig_info(sig, &info, current);
}

/*
@@ -464,7 +471,7 @@ void tick_nohz_cpu_isolated_syscall(int syscall)

pr_warn("%s/%d: cpu_isolated strict mode violated by syscall %d\n",
current->comm, current->pid, syscall);
- kill_cpu_isolated_strict_task();
+ kill_cpu_isolated_strict_task(1);
}

/*
@@ -475,7 +482,7 @@ void tick_nohz_cpu_isolated_exception(void)
{
pr_warn("%s/%d: cpu_isolated strict mode violated by exception\n",
current->comm, current->pid);
- kill_cpu_isolated_strict_task();
+ kill_cpu_isolated_strict_task(0);
}

#endif
--
2.1.2


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